Use this free online BAC calculator to estimate your blood alcohol content using the Widmark formula, based on your gender, body weight, number of standard drinks, and the hours elapsed since you started drinking. This tool is intended for general educational purposes only and must never be used to determine whether you are fit to drive.
This is an educational estimate only, not a precise measurement — actual BAC varies by individual metabolism, food intake, and other factors. Never drive after drinking, regardless of this estimate.
1 standard drink ≈ 14g of alcohol
How to Use the BAC Calculator
Select your Gender from the dropdown.
Enter your Body Weight in kilograms in the "Body Weight (kg)" field.
Enter the Number of Standard Drinks you've had (1 standard drink ≈ 14g of alcohol).
Enter the Hours Elapsed Since Drinking Started.
Click "Calculate BAC" to view your estimated blood alcohol content.
The Widmark Formula Used Here
Estimated BAC (%) = Alcohol (g) ÷ (Body weight in g × r) × 100 − 0.015 × Hours elapsed
Alcohol (g) is the number of standard drinks × 14 g.
r is the share of body weight that alcohol spreads into: 0.68 for men and 0.55 for women. Women generally have a higher proportion of body fat and less body water, so the same drink produces a higher concentration.
0.015 is an average rate at which the liver clears alcohol, in BAC percentage points per hour. The result is never shown below zero and is rounded to three decimal places.
A BAC of 0.03% means about 0.03 g of alcohol per 100 ml of blood, which is the same as 30 mg per 100 ml.
Worked Examples
A 70 kg man has 3 standard drinks and checks 2 hours after he started. Alcohol = 3 × 14 = 42 g. Peak estimate = 42 ÷ (70,000 × 0.68) × 100 = 0.088%. Subtracting 2 × 0.015 = 0.030 leaves an estimated BAC of 0.058%, almost twice India's legal driving limit.
A 55 kg woman has 2 standard drinks and checks after 1 hour: 28 ÷ (55,000 × 0.55) × 100 = 0.093%, minus 0.015 gives 0.078%. Fewer drinks, but a higher result, because of her lower body weight and distribution ratio.
Estimated Peak BAC Before Any Time Passes
Person
1 drink
2 drinks
3 drinks
4 drinks
Man, 60 kg
0.034%
0.069%
0.103%
0.137%
Man, 70 kg
0.029%
0.059%
0.088%
0.118%
Man, 80 kg
0.026%
0.051%
0.077%
0.103%
Woman, 60 kg
0.042%
0.085%
0.127%
0.170%
On these estimates, a single standard drink can bring a lighter person to or above 0.03%. Real peaks are usually reached 30 to 90 minutes after drinking and can be lower on a full stomach, but the variation between people is large.
Converting Indian Drinks to Standard Drinks
This calculator counts one standard drink as 14 g of pure alcohol. Drinks served in India rarely match that exactly, so convert them first. Grams of alcohol = volume in ml × ABV% ÷ 100 × 0.789, the density of alcohol.
Drink
Alcohol
Standard drinks
Whisky, rum or vodka, 30 ml small peg at 42.8%
10 g
0.7
Spirits, 60 ml large peg at 42.8%
20 g
1.4
Lager beer, 330 ml can at 5%
13 g
0.9
Strong beer, 650 ml bottle at 8%
41 g
2.9
Wine, 150 ml glass at 12%
14 g
1.0
Check the ABV on the label, as it varies widely. One 650 ml bottle of strong beer is close to three standard drinks, and bar pours and home-poured pegs are often larger than 30 or 60 ml.
Drink-Driving Law in India
Under Section 185 of the Motor Vehicles Act, 1988, driving with more than 30 mg of alcohol per 100 ml of blood, as detected by a breath analyser, is an offence. That is a BAC of 0.03%, stricter than the 0.05% or 0.08% used in many other countries. As of 2026, penalties after the 2019 amendments include fines, possible imprisonment and suspension of the driving licence, with heavier penalties for repeat offences. Check the current rules with your state transport department or traffic police.
Because the limit is so low and individuals vary, the only safe choice is not to drive at all after drinking. Use a cab, public transport or a driver who has not been drinking, and remember that alcohol can still be in your system the next morning.
Limitations of This Estimate
The formula assumes all alcohol is absorbed at once. In reality BAC can keep rising for some time after your last drink.
Elimination rates differ from person to person and with liver health, medicines and regular drinking habits. 0.015 per hour is only an average.
Medicines, illness, fatigue and age can make the effects of alcohol much stronger even at a low BAC. If someone is very drowsy, vomiting or hard to wake after drinking, get medical help immediately.
Frequently Asked Questions
This calculator uses the Widmark formula, which estimates blood alcohol content from the grams of alcohol consumed, your body weight, a gender-based distribution ratio (0.68 for men, 0.55 for women), and subtracts the amount your body metabolizes over time (about 0.015% per hour).
No. This BAC calculator gives an educational estimate only and does not account for individual differences in metabolism, food intake, medications, or overall health. It should never be used to determine whether you are fit to drive — never drive after drinking, regardless of this estimate.
Under Section 185 of the Motor Vehicles Act, 1988, the limit is 30 mg of alcohol per 100 ml of blood, which equals a BAC of 0.03%. On average estimates, even one or two drinks can bring some people close to or over this limit. Rules can be amended, so confirm the current position with official sources.
On the average rate used here, BAC falls by about 0.015 percentage points per hour. A peak estimate of 0.088%, for example, takes roughly 6 hours to reach zero. After a heavy night, alcohol can still be present the next morning.
No. Coffee and cold water may make you feel more alert, but they do not speed up how fast the liver removes alcohol. Eating before or while drinking slows absorption and can lower the peak, but it does not remove alcohol that is already in your blood. Only time does.